Thanks for your question. TrueNicks is a sire line nicking program that measures how well a sire line/broodmare sire line cross has fared at producing stakes winners. TrueNicks is a particularly useful research tool when planning matings, assembling a stallion's book of mares, or evaluating pedigrees of young racing prospects.

For Zenyatta, TrueNicks rates her sire Street Cry when crossed over Hail to Reason line mares as A+, with a variant of 4.61. This means that the Street Cry/Hail to Reason combination has produced stakes winners at a rate 4.61 times the average of 1.00 (TrueNicks C). This considers how Street Cry has done with mares by all other broodmare sire lines bred to him, and how mares by Hail to Reason line broodmare sires with daughters bred to Street Cry have done with all other sires. Click here to view Zenyatta's TrueNicks report.

This is not a "pedigree score" per se, but rather it describes the track record of the cross to date, considering all international starters and stakes winners. In other words, Street Cry has nicked very well with Hail to Reason line mares. As you can see in the TrueNicks report, other top horses bred on the cross are Oak Leaf Stakes (gr. I) winner Cry and Catch Me and Eclipse Stakes (gr. III) winner Southdale.

The breeder can use the TrueNicks data as a research tool while planning a hypothetical mating. When considering sending your Hail to Reason line mare to Street Cry, you now know the record that other mares of her sire line have had with Street Cry. If other factors (including – but not limited to – conformation, racing aptitudes, produce history, inbreeding, economics, etc.) are favorable, you can act confidently that the nick has had proven success. Click here for an explanation of variant scores.

Rachel Alexandra's rating of A++ represents an emerging nick that has just branched away from the successful El Prado/Forty Niner cross (TrueNicks A+), which is also responsible for grade II winner Dean's Kitten. Medaglia d'Oro/Roar is a specific cross with just three starters to date, but has shown immediate success with two stakes winners – Rachel Alexandra and multiple stakes winner She's Our Annie. While the cross is unlikely to maintain this incredible strike rate, the TrueNicks report illustrates the cross's initial success and should be a point of consideration for breeders. Click here to view Rachel Alexandra's TrueNicks report.

Also, keep in mind that the TrueNicks ratings for Zenyatta and Rachel Alexandra are not made in comparison to one another, but are relative in context to the respective sire and broodmare sire lines of each pedigree.

I hope this answers some questions about the ratings, and please feel free to comment below with any additional thoughts.